Culturing Microorganisms

What is the substance that bacteria/microorganisms are grown on called?

Culture medium

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What does the culture medium contain that is needed for the bacteria to grow?

Carbohydrates, minerals, proteins and vitamins.

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What two forms can the medium be?

A nutrient broth solution or solid agar jelly.

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What temperatures are school labs kept at when growing microorganisms? Why?

Below 25C because harmful pathogens are more likely to grow is the temperature is above this.

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What is the benefit of incubating cultures at a higher temperature?

The bacteria grows faster.

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What is an inhibition zone?

The area around a paper disc with an antibiotic where bacteria has not grown.

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When investigating the effect of an antibiotic on bacteria what is used as the control?

A paper disc that doesn't have antibiotic on it but has instead been soaked in sterile water.

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Why is this used?

To make sure that it is the antibiotic that is affecting the bacteria and not something in the paper.

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What shows which is the most effective antibiotic?

The size of the inhibition zone. The bigger the inhibition zone the more effective the antibiotic.

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How can you avoid contaminating the culture when transferring it to the petri dish?

Sterilise the inoculating loop by passing it through a flame.

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What other ways can contamination be avoided?

1. Sterilising the culture medium and petri dish(by heating at a high temperature). 2. Taping the petri dish to make sure no new bacteria goes into it from the air. 3. Store the petri dish upside down to stop condensation falling onto the jelly.